The invention is directed to vehicle brake systems having an anti-locking apparatus including a multi-position valve and a servo-pressure supply apparatus. A brake system of this kind is known from German Offenlegungsschrift No. 23 27 508. In this system, there is used a main cylinder which comes into operation if there is a failure in the servopressure supply apparatus or if there is a malfunction in an electronic amplifier system. This known system also has adjusting members for an anti-wheel-lock apparatus and further provides valves for supplying pressure to the brake system. This kind of design is relatively expensive.
A brake system without a main cylinder is also known from German Offenlegungsschrift No. 19 61 039. This known system functions with one pressure gauge at the brake pedal and one pressure gauge in the wheel brake circuit. The pressure is fed into or removed from the brake circuit by way of magnetic valves. The magnetic valves and an electronic circuit are used both for brake force amplification and for an anti-wheel-lock apparatus. This known system is again expensive. Furthermore, for safety reasons, it cannot be used in passenger vehicles, because no further braking effect is possible if there is a malfunction.